Only 4 cores working on my Ryzen 9 12-core CPU

Hello world!

I have a Ryzen 9 12-core CPU but it looks like Premiere Pro only uses 4 cores. When I for example use Warp Stabilizer, the CPU hits 15% load and 4 cores are at 50-100%, the other 8 cores are hardly moving.

The internet says that Premiere Pro uses maximum 8 cores, so shouldn't I see 4 more cores working hard with this task? Or is this normal, that is 4 cores working hard and 4 cores working "soft/supporting" the hard working cores?

The RAM is 16 GB @ 4000 MHz.